The present invention relates to a turbine stage of a gas turbine having a blow-out arrangement for blowing out a sealing gas flow into a cavity, a method for operating such a turbine stage and a gas turbine with such a turbine stage.
A turbine stage comprises a gas channel, in which most of the time a plurality of guide vane and rotor assemblies are disposed in order to transform the energy of a working gas flowing through the gas channel into torque of a rotor of the gas turbine.
Communicating with the gas channel are cavities, for example radial recesses in the rotor, in which radially inner blade tips or inner shrouds of guide vane assemblies engage. In order to reduce a leakage flow through these types of cavities, they may be delimited by one or more seals. In particular, a seal can differentiate an upstream cavity with respect to a downstream cavity in order to prevent an undesired underflowing of a guide vane assembly.
To reduce or prevent an entry of hot working gas into such cavities, blowing a sealing gas flow into the cavity is known from internal company practice. If the cavity is subject to radial blow-in, shear flows can occur at a rotor-mounted front side due to the circumferential velocity of the rotor.
One object of an embodiment of the present invention is to improve an operation of a gas turbine.
A turbine stage according to one aspect of the present invention comprises a gas channel in which one or a plurality of rotor assemblies are disposed, and through which a working gas flows during operation, in particular an exhaust gas from an upstream combustion chamber. A guide vane assembly can be disposed before and/or after at least one rotor assembly. The rotor channel can diverge in the direction of flow, at least in sections.
Communicating with the gas channel is at least one cavity, which is delimited by a front side of a single- or multi-part rotor element and by a rotor element-mounted seal.
The rotor element can comprise a rotor blade arrangement having one or a plurality of rotor blades of a rotor assembly of the turbine stage, which can be connected detachably or permanently, in particular integrally, to a rotor of the turbine stage.
In one embodiment, the front side axially delimits the cavity or forms a, in particular downstream, front wall of the cavity. In one embodiment, the seal delimits the cavity likewise axially or forms a, in particular upstream, front wall of the cavity.
In one embodiment, the cavity can be delimited radially outwardly by a further rotor element-mounted seal, through which the cavity communicates with the gas channel, in particular a labyrinth seal having one or a plurality of axial flanges, which can be opposite from one or a plurality of housing-mounted axial flanges of the turbine stage.
In one embodiment, the cavity can be delimited radially inwardly by an axial projection of the rotor element front side, in particular a seal carrier, on which the rotor element-mounted seal is disposed.
The cavity can be, in particular, a chamber between a rotor blade disk and an inner shroud of a, in particular upstream, guide vane assembly. In one embodiment, the turbine stage comprises a guide vane assembly with a radially inner counter seal, in particular an abradable lining, which is opposite from the rotor element-mounted seal and with the seal defines a sealing gap, which preferably, at least substantially, can be parallel to an axis of rotation of the turbine stage. The rotor element-mounted seal can be, in particular, a labyrinth seal having one or a plurality of radial sealing flanges, in particular radial sealing tips, which are radially opposite from the counter seal, in particular a honeycomb seal. In particular, the rotor element-mounted seal can delimit the cavity against a further, upstream cavity.
The turbine stage comprises a blow-out arrangement having one or a plurality of gas passages distributed over the circumference, preferably equidistantly, for blowing out a sealing gas flow, in particular a sealing air flow, into the cavity.
According to one aspect of the present invention, one or a plurality of, preferably all gas passages of the blow-out arrangement for blowing out the sealing gas flow, can be configured with a swirl in the circumferential direction, which in one embodiment is in the same direction as a rotational direction of the turbine stage. In this way, in one embodiment, a circumferentially swirling sealing flow can be blown-in in front of the rotor element-mounted front side so that shear flows based on the circumferential velocity of the rotor are reduced or prevented and thus, in particular, the efficiency and therefore the operation of the turbine stage can be improved.
A leakage flow can enter the cavity via the rotor element-mounted seal. This may be desired, in particular, in order to cool the rotor element, in particular the front side thereof, through the leakage flow. However, if the preferably non-swirling leakage flow directly hits the swirling sealing gas flow, the intermixture thereof can reduce the circumferential swirl of the sealing gas flow.
Therefore, according to one aspect of the present invention, an outlet opening of one or a plurality of, preferably all gas passages of the blow-out arrangement, is offset radially outwardly from the rotor element-mounted seal. The sealing gas flow is so to speak guided radially away by the blow-out arrangement through a leakage flow via the rotor element-mounted seal and first blown out radially outwardly with a swirl so that a malfunction from the leakage flow is reduced, in particular at least substantially prevented.
According to one aspect of the present invention, the sealing gas flow is accordingly blown out radially outwardly from the rotor element-mounted seal into the cavity by the blow-out arrangement with a swirl in the circumferential direction.
A gas passage can be curved in the circumferential direction for blowing out the sealing gas flow with a swirl in the circumferential direction. In addition or as an alternative, one or a plurality of deflection elements or surfaces can be disposed in a gas passage in order to apply a velocity component in the circumferential direction to the sealing gas flow flowing through the passage.
In one embodiment, a gas passage is configured as a through-borehole or continuous opening or passage of a pipe. The pipe can be produced as a separate component and be detachably or permanently fastened on the rotor element, in particular a rotor element-mounted seal carrier on which the rotor element-mounted seal is disposed, and in particular can be connected by bonding, frictionally or with a form-fit, in particular welded, adhered, soldered, locked in place, screwed together or inserted. Similarly, a pipe can also be configured integrally with the rotor element, in particular by a pipe jacket being laid open by machining around a through-borehole, in particular free milled.
In one embodiment, the pipe can extend, at least substantially, over its length, or in at least one section, preferably at least in a quarter of the length thereof next to the outlet opening, at least substantially in a plane, which is perpendicular to an axis of rotation of the turbine stage. Through this, the sealing gas flow in one embodiment can be guided in a short path through the leakage flow. In a further development, the pipe can be inclined, at least in sections, preferably at least in a quarter of the length thereof next to the inlet opening, relative to the axis of rotation of the turbine stage, in particular, in order to axially offset an inlet opening.
In one embodiment, one or a plurality of preferably all gas passages of the blow-out arrangement comprise an inlet opening, which communicates with a pressure reservoir, in particular a sealing air reservoir. In a further development, a bypass passage between the pressure reservoir and the cavity is connected in parallel in terms of flow to the blow-out arrangement. The bypass passage can be defined, in particular, by the rotor element-mounted seal, preferably a sealing gap between the seal and an opposite counter seal, in particular an abradable lining, preferably of a guide vane assembly. Therefore, in one embodiment, a pressurized gas, in particular air, preferably from a compressor upstream from the turbine stage, is guided into an upstream, further cavity and divided there into a, preferably greater, leakage flow via the rotor element-mounted seal, in particular for cooling the rotor element, and a, preferably smaller, sealing gas flow. Correspondingly, in one embodiment, the turbine stage can comprise an upstream, further cavity, which communicates with a pressure reservoir, a sealing gap via the rotor element-mounted seal and the blow-out arrangement.
A turbine stage according to the invention can be used in particular in a gas turbine, preferably an aircraft engine.
Other advantageous further developments of the present invention are disclosed in the following description of preferred embodiments.